1. Field of the Invention
The present invention relates to semiconductor packaging and, more particularly, to a dual die package (DDP).
2. Description of the Related Arts
Recent trends in electronics development have been toward smaller and thinner semiconductor packages. To satisfy the demand for smaller and thinner semiconductor packages, semiconductor packages that contain multiple semiconductor dies or chips (“multi-chip packages”) have been developed. Multi-chip packages are used in a wide variety of applications, such as in laptop computers and cellular phones. When compared with single-chip packages, multi-chip packages have the advantages of miniaturization, low weight and high mounting density. For example, it is more advantageous to use a single thin small outline package (TSOP) including a flash memory chip and a SRAM chip than a semiconductor package including the flash memory chip and another semiconductor package including the SRAM chip.
Multi-chip packages can be classified as vertical-stacking type packages or parallel-aligning type packages. Vertical-stacking type packages reduce mounting area, while parallel-aligning type packages simplify the manufacturing process and reduce package thickness. To achieve miniaturization and low weight, vertical-stacking type packages are more commonly used.
FIG. 1 is a cross-sectional view of a conventional dual die package 200, which is a vertical-stacking type package. Dual die package 200 comprises a first chip 110 and a second chip 130. First chip 110 has electrode pads 112 on a center region of its active surface, and second chip 130 has electrode pads 132 on a center region of its active surface. Second leads 141 are mechanically connected to the active surface of second chip 130 via an adhesive 152, and first leads 121 are mechanically connected to the active surface of first chip 110 by an adhesive 152.
Second chip 130 is attached to the bottom surfaces of second leads 141 such that electrode pads 132 are located between the opposite second leads 141, and first chip 110 is attached to the bottom surfaces of first leads 121 such that electrode pads 112 are located between the opposite first leads 121. The back surfaces of first chip 110 and second chip 130 face one another and are disposed between first leads 121 and second leads 141.
First leads 121 comprise first contact portions 123 and first connection portions 125. First connection portions 125 are stepwise connected to first contact portions 123. Second leads 141 comprise second contact portions 143 and second connection portions 145. Second connection portions 145 are stepwise connected to second contact portions 143.
Electrode pads 112 of first chip 110 are electrically connected to first contact portions 123 via bonding wires 162, and electrode pads 132 of second chip 130 are electrically connected to second contact portions 143 via bonding wires 164. First chip 110, second chip 130 and the electrical connection parts are encapsulated with an encapsulant, thereby forming a package body 180.
First connection portions 125 of first leads 121 and second connection portions 145 of second leads 141 are mechanically attached to each other and electrically connected to each other. Outer lead portions (not shown) of first leads 121 are cut and removed. Outer lead portions 149 of second leads 141 are bent in a predetermined shape so that they can be mounted and serve as external connection terminals. After forming a metal layer 170 made of a metal such as solder or silver (Ag) on first connection portions 125 and second connection portions 145, the first connection portions 125 are attached to the corresponding second connection portions 145 using a thermocompression process carried out at a predetermined temperature and pressure. The thermocompression process mechanically and electrically connects first connection portions 125 and second connection portions 145.
One disadvantage with manufacturing conventional dual die package 200 is that the step of forming metal layer 170 on first leads 121 and second leads 141 and the step of attaching first leads 121 and second leads 141 using a thermocompression process to each other require additional manufacturing equipment, which increases the production cost of conventional dual die package 200. Another disadvantage with manufacturing conventional dual die package 200 is that the thermocompression process used to attach the first leads 121 of the first lead frame 120 to the second leads 141 of the second lead frame 140 requires highly reliable attaching technology, which increases the production cost of conventional dual die package 200.
Accordingly, what is needed is an improved dual die package.